Researchers at Aalto University’s Department of Applied Physics have, for the first time, connected time crystals to another system external to itself.
The study describes how the team turned a time crystal into an optomechanical system that could be used to develop things like extremely accurate sensors or memory systems for quantum computers, significantly boosting their power.
Jere Mäkinen, who led the study, explained: “Perpetual motion is possible in the quantum realm so long as it is not disturbed by external energy input, such as by observing it.
“That is why time crystals had never before been connected to any external system. However, we did just that and showed, also for the first time, that you can adjust the crystal’s properties using this method.”
A brief history of time crystals
A glittering hunk of crystal gets its iridescence from a highly regular atomic structure. Frank Wilczek, the 2012 Nobel Laureate in Physics, proposed that quantum systems could construct themselves in the same way, but in time instead of space.
He dubbed such systems time crystals, defining them by their lowest possible energy state, which perpetually repeats movements without external energy input.
Therefore, these crystals were experimentally proved to exist in 2016.
Observing changes in the frequency of time crystals
The researchers used radio waves to pump magnons into a Helium-3 superfluid cooled to near-absolute zero.
When the team turned off the pump, the magnons formed a time crystal that stayed in motion for an unprecedentedly long time, lasting up to 108 cycles or several minutes before fading down to a level the researchers could no longer observe.
During the fading process, the crystal connected itself to a nearby mechanical oscillator in a way determined by the oscillator’s frequency and amplitude.
“We showed that changes in the time crystal’s frequency are completely analogous to optomechanical phenomena widely known in physics,” Mäkinen stated.
“These are the same phenomena that are used, for example, in detecting gravitational waves at the Laser Interferometer Gravitational-Wave Observatory in the US.
“By reducing the energy loss and increasing the frequency of that mechanical oscillator, our setup could be optimised to reach down near the border of the quantum realm.”
Implications for quantum computing
This research demonstrates that time crystals have the potential to enhance quantum computing and sensing capabilities significantly.
Mäkinen concluded: “Time crystals last for orders of magnitude longer than the quantum systems currently used in quantum computing. The best-case scenario is that they could power the memory systems of quantum computers to significantly improve them.
“They could also be used as frequency combs, which are employed in extremely high-sensitivity measurement devices as frequency references.”